Light can be used to obtain a read out of physical parameters. Some applications of this principle are used in resonant transmission of infra-red, terahertz (THz) radiation for communication or optical cavities or interferometers. However, present applications use metallic and dielectric gratings to leverage these optical effects.
Another option is to use gratings. Gratings are optical periodic elements with properties of dispersing and diffracting light. When the period of the grating is below the wavelength of normally incident light, diffraction orders are non-existent, but non-propagating evanescent waves exist parallel to the grating surface. However, these evanescent waves are not detectable by traditional optics because the energy decays exponentially to a negligible level within a micron from the grating surface. Thus, the use of a single grating presents challenges for using light to obtain read out of physical parameters.